Many types of heat exchangers in use today employ two spaced header and tank constructions. Generally parallel, open ended tubes interconnect the header and tank constructions and are in fluid communication with the interior of each. In many cases, plate or serpentine fins are disposed across the tubes between the header and tank constructions. Typical examples of such heat exchangers are vehicular radiators and condensers, although such heat exchangers may be found in many other applications as well.
In manufacturing heat exchangers of this type, holes must be formed in the header surfaces of each of the header and tank constructions to receive the ends of the tubes. Most frequently this is accomplished by a punching operation wherein material is actually removed from the header surface at the hole location, but even where the hole is formed simply by piercing and deformation without material removal, the resulting lack of continuity in the header surface weakens the same.
Those skilled in the art will readily recognize that heat exchangers of the sort of concern are pressurized, that is, the heat exchange fluid within the tubes and the heater and tank constructions will be subjected to an elevated pressure. Because the header surface in the area of the holes is weakened during the formation of the holes, such elevated pressure may cause deformation in those areas. The deformation, in turn, can result in the formation of leakage openings at the joints between the tubes and the header surface. If the elevated pressure becomes extreme, rupture of the header surface can also occur.
The present invention is directed to overcoming one or more of the above problems.